pkg/planner: avoid eliminating max/min over binary literals

pkg/planner/core/issuetest/planner_issue_test.go

@@ -545,6 +545,37 @@ HAVING EXISTS (SELECT 1 FROM t_panic WHERE x IS NULL);`).Check(testkit.Rows("<ni
 		tk.MustQuery("select * from t1;").Check(testkit.Rows("1 <nil> "))
 	}
 
+	// abs-max-binary-literal-group-by-unique-key
+	{
+		tk := prepareSharedTestKit(t)
+		expectedRows := testkit.Rows("0")
+		expectedWarnings := testkit.RowsWithSep("|", "Warning|1292|Truncated incorrect DOUBLE value: '*'")
+		runQuery := func(createTableSQL, query string) (rows, warnings [][]any) {
+			t.Helper()
+			tk.MustExec("drop table if exists t0")
+			tk.MustExec(createTableSQL)
+			tk.MustExec("insert ignore into t0 values (1)")
+			rows = tk.MustQuery(query).Rows()
+			warnings = tk.MustQuery("show warnings").Rows()
+			return
+		}
+
+		for _, aggFunc := range []string{"max", "min"} {
+			query := fmt.Sprintf("select abs(%s(b'101010')) as c3 from t0 as tom8 group by tom8.c0", aggFunc)
+			uniqueRows, uniqueWarnings := runQuery("create table t0(c0 numeric zerofill not null unique)", query)
+			plainRows, plainWarnings := runQuery("create table t0(c0 numeric)", query)
+
+			require.Equalf(t, expectedRows, uniqueRows,
+				"aggFunc=%s uniqueWarnings=%v", aggFunc, uniqueWarnings)
+			require.Equalf(t, expectedRows, plainRows,
+				"aggFunc=%s plainWarnings=%v", aggFunc, plainWarnings)
+			require.Equalf(t, expectedWarnings, uniqueWarnings,
+				"aggFunc=%s uniqueRows=%v", aggFunc, uniqueRows)
+			require.Equalf(t, expectedWarnings, plainWarnings,
+				"aggFunc=%s plainRows=%v", aggFunc, plainRows)
+		}
+	}
+
 	// join-reorder-adds-selection
 	{
 		tk := prepareSharedTestKit(t)

pkg/planner/core/rule_aggregation_elimination.go

@@ -177,7 +177,14 @@ func rewriteExpr(ctx expression.BuildContext, aggFunc *aggregation.AggFuncDesc)
 			return true, wrapCastFunction(ctx, aggFunc.Args[0], aggFunc.RetTp)
 		}
 		return true, rewriteCount(ctx, aggFunc.Args, aggFunc.RetTp)
-	case ast.AggFuncSum, ast.AggFuncAvg, ast.AggFuncFirstRow, ast.AggFuncMax, ast.AggFuncMin, ast.AggFuncGroupConcat:
+	case ast.AggFuncMax, ast.AggFuncMin:
+		// MAX/MIN over binary literals preserve string-like aggregation semantics.
+		// Rewriting them to a projection changes downstream cast and warning behavior.
+		if expression.IsBinaryLiteral(aggFunc.Args[0]) {
+			return false, nil
+		}
+		return true, wrapCastFunction(ctx, aggFunc.Args[0], aggFunc.RetTp)
+	case ast.AggFuncSum, ast.AggFuncAvg, ast.AggFuncFirstRow, ast.AggFuncGroupConcat:
 		return true, wrapCastFunction(ctx, aggFunc.Args[0], aggFunc.RetTp)
 	case ast.AggFuncBitAnd, ast.AggFuncBitOr, ast.AggFuncBitXor:
 		return true, rewriteBitFunc(ctx, aggFunc.Name, aggFunc.Args[0], aggFunc.RetTp)